Light weight flexible high voltage bushing



Jan. 31, 1967 H. A. FREY LIGHT WEIGHT FLEXIBLE HIGH VOLTAGE BUSHINGFiled Sept. 29, 1965 2 Sheets-Sheet l Jan. 31, 1967 H. A. FREY 3,301,938

LIGHT WEIGHT FLEXIBLE HIGH VOLTAGE usnme Filed Sept 29, 1965 2Sheets-Sheet 2 United States Patent 3,301,938 LIGHT WEIGHT FLEXIBLE HIGHVOLTAGE BUSHING Howard A. Frey, Towson, Md., assignor to GeneralElectric Company, a corporation of New York Filed Sept. 29, 1965, Ser.No. 491,162 Claims. (Cl. 17431) This invention relates to electricbushings and more particularly to a light weight flexible high voltagebushmg.

In carrying high voltage lines through grounded barriers of varioustypes, electrical bushings must be employed to insulate the high voltagelead from ground. Conventional bushings for this purpose have been madeby a variety of methods. Present designs for high voltage bushings,however, almost invariably involve rigidity in the bushing member andrelatively high weight. For example, a bushing capable of being used forcarrying 900 kv. D.C. conductor through a grounded barrier wouldprobably weigh something of the order of 6,000 pounds.

In accordance with this invention, a bushing is provided in which theprime insulation is pressurized gas contained in a flexible, inflatedand distended housing or shell which maintains the relative orientationor operative spacing of the conductive parts of the bushing which are atdifferent potential.

An object of the invention is to provide a new and improved electricbushing.

Another object of the invention is to provide a light weight, flexiblehigh voltage bushing.

A further object of the invention is to provide a gas filled bushinghaving a flexible, inflated housing which maintains the relativeorientation or operative spacing of the conductive parts of the bushingwhich are at different potential.

The invention will be better understood from the following descriptiontaken in connection with the accompanying drawing and its scope will bepointed out in the appended claims.

In the drawings:

FIG. 1 is an elevation view partly in section of an embodiment of theinvention,

FIG. 2 is a similar view of a modification, and

FIG. 3 is a similar view of another modification in which a relativelylight rigid stiffening element is used to help support the flexiblecovering.

Referring now to the drawings and more particularly to FIG. 1, thebushing comprises a conducting tube 1 made of sheet metal of the minimumgauge required for the current carrying capacity of the bushing. Thisconducting member 1 is surrounded by a torus 2 made of light sheet metaland so proportioned that the relationship between the inside diameter ofthe torus and the outside diameter of the conducting tube produces afield of controlled intensity at the required operating voltage. Methodsof calculating the field of such concentric electrodes is wellestablished in the art. This gap is enclosed with a sheet material 3such as vinyl coated nylon. Teflon coated nylon, rubber coated canvas orsimilar materials which are common articles of commerce. As shown, thematerial 3 is in the form of a pair of frustoconical shells attached attheir large ends in any suitable manner to the torus 2 and at theirsmall outer ends in any suitable manner to the tube 1.

The bushing is inflated with any suitable dielectric gas through aninlet valve 4, the gas passing from the interior of the torus 2 into theinterior of the bushing through a hole 5 in the wall of the torus. Thegas may be either an or an electronegative gas such assulfurhexafluoride under sufficient pressure to obtain the finallyrequired electrical characteristics in the gap and the required firmnessof the structure so as to maintain the coaxial relationship between thetube 1 and the torus 2.

In the modification shown in FIG. 2, additional external leakagedistance is provided so that the bushing will not flash-over or leakexcessively under rain or other conditions of surface contamination ofthe sheet material comprising the housing of the bushing. This is doneby corrugating or pleating the bushing as shown. This can beaccomplished by cutting rings 6 of the sheet material and fastening themtogether at their respective inner and outer edges using techniqueswhich are well known.

Another feature of FIG. 2 is that the weight is further reduced byeliminating the central metallic ground sleeve torus 2 and merelycoating the equitorial part of the flexible housing with a conductivespray or paint 7.

In the modification shown in FIG. 3, a comparatively light weight rigidinsulating tube 8 is provided for backing up the outer covering offlexible sheet material. The cylinder 8 may be formed of any suitablematerial such as wound resin impregnated paper. As shown, it is providedwith a plurality of holes 9 through which the gas can pass for inflatingthe outer flexible covering which can be similar to that shown in FIGS.1 or 2. In this figure, the central ground portion is shown as a ring 10of conducting material such as light gauge metal.

While there have been shown and described particular embodiments of theinvention, it will be obvious to those skilled in the art that changesand modifications may be made without departing from the invention, andtherek fore it is intended by the appended claims to cover all suchchanges and modifications as fall within the true spirit and scope ofthe invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. An electrical bushing comprising, in combination, a pair of outershells of flexible insulating sheet material attached at one of theirends to and extending in opposite directions from a circular conductiveground ring and attached at their opposite ends to the ends of acylindrical conductor extending through the center of said ringperpendicular to the plane of the latter, said shells normally beinginflated and distended by an insulating gas under pressure filling thespace in said bushing between said cylindrical conductor on the one handand said shells and ground ring on the other hand so as flexibly tomaintain the relative orientation of the conductive parts andconstituting the entire outer insulating surface of said bushing.

2. A bushing as in claim 1 in which said shells are pleated to increasethe external leakage distance over their surface between the conductiveparts, said pleating being produced by making said shells of a pluralityof coaxial rings of inelastic sheet material with the outer edge of eachring hermetically joined to the outer edge of an adjacent ring and theinner edge of each ring hermetically joined to the inner edge of anadjacent ring.

3. A bushing as in claim 1 in which said shells are backed internally bystiflening elements of relatively rigid light weight insulation materialpervious to said gas.

4. A bushing as in claim 1 in which the material of said shells issubstantially inelastic.

5. A bushing as in claim 1 in which said ground ring is a conductiveouter coating on a central web of flexible sheet material, integrallyjoining said one end of said shells.

References Cited by the Examiner FOREIGN PATENTS 880,275 10/ 1961 GreatBritain.

LARAMIE E. ASKIN, Primary Examiner.

1. AN ELECTRICAL BUSHING COMPRISING, IN COMBINATION, A PAIR OF OUTERSHELLS OF FLEXIBLE INSULATING SHEET MATERIAL ATTACHED AT ONE OF THEIRENDS TO AND EXTENDING IN OPPOSITE DIRECTIONS FROM A CIRCULAR CONDUCTIVEGROUND RING AND ATTACHED AT THEIR OPPOSITE ENDS TO THE ENDS OF ACYLINDRICAL CONDUCTOR EXTENDING THROUGH THE CENTER OF SAID RINGPERPENDICULAR TO THE PLANE OF THE LATTER, SAID SHELLS NORMALLY BEINGINFLATED AND DISTENDED BY AN INSULATING GAS UNDER PRESSURE FILLING THESPACE IN SAID BUSHING BETWEEN SAID CYLINDRICAL CONDUCTOR ON THE ONE HANDAND SAID SHELLS AND GROUND RING ON THE OTHER HAND SO AS FLEXIBLY TOMAINTAIN THE RELATIVE ORIENTATION OF THE CONDUCTIVE PARTS ANDCONSTITUTING THE ENTIRE OUTER INSULATING SURFACE OF SAID BUSHING.